Wall cap for ventilating duct



April 30, 1957 R. PRYNE 2,790,377

WALL CAP FOR VENTILATING DUCT Filed July 24, 1955 14 7'70 NEYS- United States Patent WALL CAP FOR VENTILATING DUCT Ralph Pryne, Pomona, Calif., assignor to Pryne & (30., Inc., Pomona, Calif., a corporation of California Application July 24, 1953, Serial No. 370,030

8 Claims. (Cl. 98-119) The present invention relates generally to ventilating apparatus and equipment and relates more especially to a protective closure for the end of a ventilating duct.

Protective closures of this type are commonly called wall caps.

Ventilating fans and blowers frequently have horizontally extending exhaust ducts, or at least the duct has a horizontal section passing through a vertical wall. The open end of this duct needs to be protected not only against the entry of wind and rain but also against entry of convection currents which would create back draft in the duct. For this purpose a pivotally mounted shutter is provided at the end of the duct, the shutter swinging by gravity to a position closing the end of the duct.

It is the general object of my invention to improve the eifectiveness and the operation of the closure means at the end of the duct.

It is also an object of my invention to provide. an improved design fora wall cap by which wind blowing into the wall cap is deflected to exert a force on the shutter tending to close the shutter.

It is the further object of my invention to provide an improved design for a wall cap in which the outside air currents are prevented from passing round the shutter thereby tending to open it but are rather utilized to close the shutter.

These and other objects of my invention are attained in a wall cap having a housing on which a top-pivoted shutter is mounted to close an exhaust duct, by providing a deflector which is spaced from the shutter and adapted to deflect the wind or air currents against the shutter. These currents move the shutter away from the deflector and toward the closed position. It is preferable to provide a flange along the lower edge of the shutter which not only catches the air currents directed against the shutter by the deflector but also itself acts as a deflector to exert a pressure on,.the shutter moving it-to closed position. 'Thedeflector is mounted below the hood portion of the housing and spaced from it and from the shutter so that both the upper and lower faces of the deflector are operative to direct air currents against the shutter.

How the above objects and advantages of my invention, as well as others not specifically referred to, are attained will be more readily understood by reference to the following description and to the annexed drawings,

in which: a W

Fig. 1 is a perspective view of a wall cap constructed according to my invention and mounted on the outside face of a wall at the end of an exhaust duct; 7

Fig. 2 is a vertical section through my improved wall cap, on line 2-2 of Fig. 4; r

Fig. 3 is a bottom view of my improved wall cap; and

Fig. 4 is an elevation of the inlet side of the wall cap, as viewed from the right in Fig. 2. i

A wall cap, indicated generally at in Fig. l, is ordinarily mounted at the outside of an exterior wall 11 2,790,377 Patented Apr. 30, 1957 'ice in a position to close the outlet end of exhaust duct 12. Duct 12 discharges to the atmosphere air which is forced through the duct by a fan 14, or other similar means.

The housing of the wall cap is provided with an attaching flange 15 by which the wall cap is fastened to elements of wall 11 or other suitable supporting means. The rear face of attaching flange 15 is preferably flat to aid in mounting the wall cap on the wall which usually is vertical. Disposed centrally of and surrounded by this attaching flange, is a rectangular opening 16 which is the inlet to the wall cap from duct 12. Flange 17 of rectangular outline projects inwardly from attaching flange 15 and also extends entirely around this inlet opening to provide a means for connecting the housing to duct 12, this connection ordinarily being a sliding fit with the duct.

On the front or outer side of opening 16, there is located shutter 20 which is pivotally connected at 21 at its top edge to the housing. Under the influence of gravity, the shutter normally hangs down in a vertical position, or substantially so, in which it engages the wall of the housing around inlet 16 to close opening 16, as shown in full lines in Fig. 2. Shutter 20 is made of thin gauge metal and can swing freely outwardly to some such position as shown in dot-dash lines in Fig. 2, under the pressure of air being exhausted through duct '12, in order to allow exhausted air to flow out through the wall cap. A felt gasket 22 is preferably placed on the housing Along the bottom edge of shutter 20 is a flange 24 which extends across the full width of the shutter. The flange extends upwardly and outwardly from the lower edge of the shutter for a short distance, thus making an 7 acute angle with the face of shutter 20 away from inlet 16.

The housing of the wall cap includes a hood 26 which extends generally downwardly and outwardly from a position just above the top of inlet opening 16 and shutter 20. The hood includes side or end walls 26a in order to completely shield the shutter and the opening a where it is spaced below the lower edge of hood 26, as

shown particularly in Fig. 2, and it is spaced outwardly from shutter 20. Deflector 30 is a flat member having at least its upper surfaceplanar and lying in la plane at approximately 4'5 to. the vertical or to the position of the shutter when closed so that the surface is inclinedupwardly toward the shutter. Deflector'30 is preferabiy a thin, slreetmetal member'having parallel planar faces at opposite sides. flector may be varied at least 10f either Way from this position, since with different proportions of the pantsits position with respect to the shutter may be changed and accordingly its most effective angle to deflect air currents against the shutter maydiffer somewhat from that shown.

It is also preferable to add a bafile immediately below inlet opening 16 and extending across the full width of the shutter. This baffle may take the form of'angle member 32, one leg of the angle extending substantially horizontally away from inlet 16 just below the lower edge !of the shutter when closed as in Fig. 2.

When the wind blows towardthe wall cap, that is from the left as viewed in Figs. 1 and 2, a portion of the air entering hood 26 passes underneath the lower edge of the hood and strikes against the upper inclined surface of deflector 30. This air is then deflected upwardly and However, the inclination 'of this de moves in the direction of arrow 33 to blow against the face of shutter 20 away from inlet opening 16. If the air is deflected sharply upwardly, it strikes against hood 26 and is again deflected before it reaches the shutter. Some of the wind striking the surrounding area, on the wall 11, may create an upwardly moving current of air which enters the open underside of hood 26. A portion of this current strikes against the inclined underside of deflector 3i and is thereby deflected against the face of shutter 20 away from inlet 16 as indicated by arrow 34.

Since the air under the hood can only escape through the same two openings by which it enters, there is no general air movement through the housing. Rather the kinetic energy of the air currents is dissipated and a small pressure of static nature is built up against the face of the shutter exposed to the interior of the housing. This effect is increased by flange 24 which catches air moving downwardly over the face of the shutter and directs it away from the shutter.

It should also be noted that air moving upwardly through the outlet opening of the housing strikes against the inclined lower face of flange 24. The reaction to the force of this air is in a direction to move shutter 29 toward its closed position, Hence, not only the air striking against the lower face of flange 24 but also the air blowing against the outside face of shutter 26 'exert forces on the shutter itself which move the shutter toward a closed position.

Baifle 32 prevents upwardly moving air currents from blowing between the lower edge of the shutter and the housing where the shutter rests against felt gasket 22. For instance, at this point air moving generally parallel to the shutter, might force it open slightly and enter duct 12;'b.ut this situation is prevented by battle 32 which directs the air outwardly away from the shutter.

From the foregoing description, it can be seen that various changes may be made in the exact arrangement and positioning of the various parts of my improved Wall cap without departing from the spirit and scope of any invention; and accordingly itis to be understood that the foregoing description is considered as illustrative of,

rather than limitative upon, the appended claims.-

lclaim:

l. A wall cap for an exhaust duct comprising: a housing having wall means defining an inlet at one side of the housing disposed in a substantially vertical plane and also defining a downwardly facing outlet at the underside of the housing; a shutter pivotally mounted within the housing, said shutter being gravity biased toward a position engaging the Wall means at the inlet to close the inlet and movable away from the wall means and into the housing to open the inlet; and a deflector mounted on the housing and spaced below one wall of the housing at a position spaced from the shutter, said deflector having a surface inclined upwardly toward the shutter to deflect air currents against the face of the shutter away from the inlet and thereby urge the shutter toward the inlet and said closed position.

2. A wall cap'as in claim 1 in "which the deflecor is a'sheet metal member having parallel planar faces at V opposite sides.

3. A wall cap as in claim 1 that also includes a flange vmounted on the shutter face away: from the inlet, the

flange projecting upwardly and outwardly from said face of the shutter at an'acute angle to catch air currents moving downwardly'over said face of the shutter.

4. A wall cap as in claim 3 that also includes a horizontally extending baflle mounted on the housing below said inlet to the housing, the baflie projecting away from the inlet for a lesser distance than the flange to shield the lower edge of the shutter against upwardly moving air currents.

5, A wall cap as in claim 1 that also includes a flange mounted on the shutter face away from the inlet, the flange projecting upwardly away from the shutter and having an upwardly inclined under surface disposed above the outlet of the housing and against which upwardly moving currents entering through the outlet strike.

6. A wall cap for an exhaust duct comprising: a housing having wall means defining an inlet at one side of the housing disposed in a substantially vertical plane, a hood extending downwardly and outwardly away from the top of the inlet, and end walls adjoining said wall means and the hood to define a downwardly facing outlet in the housing; a shutter pivotally mounted within the housing, said shutter being gravity biased toward a posi tion engaging the wall means to close the inlet and movable away from the wall means and into the housing to open the inlet; and a deflector mounted on the housing below and spaced from the lower edge of the hood, said deflector having a surface inclined upwardly toward the shutterto deflect air currents striking against said surface upwardly into the interior of the hood and against the upper portion of said face of the shutter to urge the shutter toward the closed position.

7'. A wall cap as in claim 6 in which the deflector is located at one side of the outlet and has upper and lower surfaces disposed at about 45 to the vertical which surfaces respectively deflect horizontally and upwardly moving air currents.

8. A wall cap for an exhaust duct comprising: a housing having wall means defining an inlet at one side of the housing disposed in a substantially vertical plane, a hood extending downwardly and outwardly away from the top of the inlet, and end walls adjoining said wall means and the hood to define a downwardly facing outlet in the housing; a shutter pivotally mounted within the housing,

said shutter being gravity biased toward a position engaging the wall means to close the inlet and movable away from the wall means and into the housing to open the inlet; a flange mounted on the shutter face away from the inlet, the flange projecting upwardly and outwardly from said face of the shutter at an acute angle to catch air currents moving downwardly over said face of the shutter; and a horizontally extending baffle mounted on the housingbelow said inlet to the housing, the baflle projectingaway from the inlet for a lesser distance than the flange to shield the lower edge of the shutter against upwardly moving air currents.

' I ReferencsCitd in the file'of this patent Great Britain 1914 

